SINGAPORE - The North-South MRT line has been hit with a glitch on Friday (June 2), the second day in a row this has happened.

On its Facebook page, SMRT said: "Due to a signalling fault, North-South Line (NSL) train services in both directions between Kranji and Admiralty stations have been running at a slower speed since 5:05pm.

"NSL commuters are advised to add about 30 minutes to their journey. Free bus and bus bridging services are available between Choa Chu Kang and Yishun.

"Our engineers are working to rectify the situation. We are sorry for the inconvenience caused."

In an update at 5.55pm, it said: "Train services in both directions from the city area to Yishun MRT station, and from Jurong East to Choa Chu Kang MRT stations are still available. However, commuters should allow for additional travelling time due to evening peak."

This incident came just a day after the same line was disrupted by the trial of a new signalling system. SMRT had described it as a "new signalling system check" then.

The Straits Times understands the fault has to do with a fault in the system's main server. The new signalling system was installed by Thales. ST also understands that trains are moving at 18kmh.

Neither SMRT or the Land Transport Authority could comment when asked how long the testing period would last.

There were announcements in both English and Chinese at stations and inside the train cabins when The Straits Times took the North-South Line, between Bishan and Ang Mo Kio.

Staff on the Ang Mo Kio platform were present to guide commuters.

The transport operator posted an update on Twitter at 5.35pm, directing commuters to an online directory that listed "alternative travel options" from MRT stations.

"In the event of a train disruption, we encourage commuters to seek alternative travel options," said SMRT in the directory.

At 5.56pm, SMRT said in an update on its Facebook page that "train services in both directions from the city area to Yishun MRT station, and from Jurong East to Choa Chu Kang MRT stations are still available".

"However, commuters should allow for additional travelling time due to evening peak," it said.

When The Straits Times took the train at 6pm, the train was still staggering towards Yishun from Khatib. A typical three-minute journey took close to 10 minutes, more than double the time.

Commuters were told to alight at Yishun station, where staff were seen giving out pamphlets to advise passengers on the alternative modes of transport available.

Crowds of commuters were seen spilling onto the roads to board the free shuttle bus services.

SMRT said at 7.56pm that the fault was cleared and train services were progressively returning to normal.